Plug for ball point pen ink reservoir tube and method of making same



2,804,049 PLUG FOR BALL POINT PEN INK RESERVOIR TUBE H. W. SAME AND METHOD OF MAKING SAME Filed July 29, 1954 93 Fig 6 IN VEN TOR.

Aug. 27, 1957 By 359552; m JAMS 72?.

mmor PLUG FOR BALL POINT PEN INK RESERVOIR TUBE AND METHOD OF MAKING SAME Herbert W. Sams, Atlanta, Ga., assignor to Scripto, Inc, Atlanta, Ga., a corporation of Georgia Application July 29, 1954, Serial No. 446,461 3 Claims. or. 120-424 This invention relates to plugs for ball point pen ink tubes and more particularly to an improved form of plug and method for producing same whereby an air vent aperture can be formed in the plug sufficiently minute in size to avoid leakage of ink through the aperture when the pen is inverted and even when a dry socket condition is established at the ball point, as described further below.

The problem of preventing leakage of ink from the end of a ball point pen ink tube remote from the ball point varies widely, depending upon usage of the pen, e. g., the extent to which the pen is inverted or the ball point used at a higher elevation than the opposite end of the pen. This condition commonly occurs when the pen is placed loosely in a pocket or pocketbook, as distinct from being attached by the clip in an upright position. If :the pen remains in this position for an extended length of time and the ink tube has a sufficiently large diameter, the ink will leak out of the end of the :tube opposite the ball point.

This problem is made more acute when .a dry socket is established at the ball point. A dry socket often occurs when the pen is used for writing in an inverted or upwardly slanting position such as when writing on a wall, or when the pen is placed in a pocket or pocketbook with the ball point exposed and the ink on the ball and in the ball socket wiped off by the fabric or other material with which it comes in contact. When this occurs, atmospheric pressure is established on-the ink column at the ball point end of the ink tube and this increases substantially the tendency of the ink to leak from the opposite end of the tube due to hydrostatic pressure. Under this condition, it becomes necessary to place a plug in the end of the ink tube opposite :the ball point to prevent leakage of the ink therefrom, but at the same time pro vide an opening in the plug which will permit air to enter that end of the tube and cause the ink to flow properly through the tube to the ball point as it is used up in writing. When a plug is used the problem then arises of providing a hole sufficiently small to prevent leakage of the ink through the hole and yet permit air to enter.

The usual form of plug used heretofore for this purpose is of solid or one-piece construction made of metal or other suitable material, and has a hole drilled or machined in the plug. Practical limitations prevent forming a hole in this manner small enough to prevent the escape of ink due to a dry socket. When a dry socket occurs and atmospheric air pressure is thus established at the ball point end of the tube, the ink will escape through any size hole that can be economically produced by drilling. Thus, to prevent the escape of ink through air vent holes under dry socket conditions requires an improved method and means over those heretofore used or available and something substantially diiferent from a drilling or machining procedure for forming the holes. Under dry socket conditions it is necessary, I have found, to provide a hole of cross sectional area equal approximately to that of a hole 0.003 in diameter and preferably smaller. A hole of this minute dimension cannot be satisfactorily produced nite States Patent by the usual machining methods or means, and a feature of my invention is the povision of a new method and means that will answer this problem and in fact is well adapted for producing tiny holes.

By this improved method and means, I am able to produce holes as swall as .000002 square inch in cross sectional area. In accordance with the procedure and the form of plug that characterize my invention, the air vent hole or opening has a cross sectional area not exceeding .000006 square inch. Also, in this particular arrangement, the length of the hole may be conveniently made from the preferred minimum of A" to approximately 1" or more. A hole of these minute dimensions and length could not possibly or practically be formed in the usual solid plug by the usual means.

The above-mentioned substantial improvements that characterize my invention are obtained by molding the plug from flexible plastic such as, for example, polyethylene, vinyl plastics or rubber, and using an elongated, two-part plug construction adapted to be folded upon itself so that the two mating halves when connected in face-to-face relationship will produce a cylindrical plug of a size and shape suitable for inserting in the end of the ink tube opposite the ball point. The opening or openings in this form of flexible plastic plug are provided by means of a knife-like projection in the mold that forms a minute groove or channel in one or both halves of the mating pieces that form the plug. This type of groove or channel opening can be provided of a size not to exceed the above-mentioned .000006 square inch and of any suitable length required for the viscosity of the particular ink used and which varies from about 3,000 to 12,000 centipoises at 77 F., with diiferent inks.

Another advantageous feature of the improved plug of my invention is its use in conjunction with the socalled grease seals for ball point pen ink tubes. These small deposits of grease in the end of the ink (tube opposite the ball point will normally prevent the escape of ink from that end of the tube, but under cretain conditions even these grease seals are not effective for preventing leakage of ink. vFor example, if the grease seal becomes broken, as may occur when the ink supply is diminished, and a dry socket condition is established at the ball of the pen such that atmospheric air pressure is admitted to that end of the ink column, the disrupted grease seal and ink will escape through any hole that can be economically produced by drilling or machining, and in fact will escape through an air vent aperture much smaller in size. The fact that the air vents can be formed according to my invention of practically infinitesimal size makes the plug of this invention eifective for preventing leakage of the grease seal or ink or both under even these most adverse conditions.

Further features of my invention will be understood from the following more detailed description taken in conjunction with the accompanying drawings, in which:

Fig. l is an elevation, partly broken away, of a ball point ink reservoir tube fitted with a rear end plug formed in accordance with the present invention;

Fig. 2 is an enlarged sectional detail of the rear end portion of the ink tube and plug therein;

Fig. 3 is a section taken substantially on the line 3-3 in Fig. 2;

Fig. 4 is a plan view of the plug;

Fig. 5 is .a right side view corresponding to Fig. 4; and

Fig. 6 is an end view as seen from the top in Fig. 5.

In the drawings, the improved plug of the present invention is indicated generally by the reference numeral 10, and is shown in Fig. l as it appears inserted in place at the rear end of a conventional form of ink reservoir 12. As shown, the plug 10 comprises a unitary element which is formed of a flexible plastic material so that it may be doubled .at an intermediate shank portion 14 to mate end portions 16 and 18 thereof in the form of a composite cylindrical plug body.

Figs. 2 'and 3 illustrate the form of this plug body in enlarged detail as being formed by the mated disposition of the end portions 16 and 18, which are semi-circular in cross section and therefore complementary components of the plug body. The end portions 16 and 18 are connected by the intermediate shank portion 14, and this shank portion 14 is notched as at 20 midway of its length and oppositely with respect to the mating faces of the end portions 16 and 18 to provide for doubling of the end portions readily into mated relation. Also, as previously noted, one of the end portions 16 is preferably formed with a recess 22 and the other end portion 18 with a locating lug 24 for maintaining the mated relation of the end portions as the plug 10 is inserted within the rear end of the ink tube 12. A

One of these end portions, preferably the end portion 18, is further formed with at least one groove as at 26 in the mating face thereof that extends throughout the length of this end portion and that is smaller in cross section than will allow ink to flow therethrough. A small groove of this sort can be readily formed in a plane surface such as is provided by the mating face of the end portion 18, and such a groove serves to excellent advantage as an air vent when incorporated in the plug structure provided by the present invention.

Figs. 4, and 6 of the drawings further illustrate the unitary structure of the plug of the present invention, and show its initial form before doubling for insention in the ink tube 12.

The specific dimensions of the minute groove 26 referred to in the foregoing specification are not claimed in the present application, but a groove is further disclosed and claimed in applicants 'copending application, Serial No. 476,479, filed December 20, 1954.

The present invention has been described in detail above for purposes of illustration only and is not intended to be limited by this description or otherwise except as defined in the appended claims.

I claim:

1. A plug adapted for insertion at the rear end of a ball point ink reservoir tube to prevent leakage of ink at said rear tube end while venting the rear end of the tube to the atmosphere, said plug comprising a unitary flexible plastic element having an intermediate shank portion connecting mating end pontions of complementary circular segment cross section with at least one of said end portions having a groove extending throughout the length thereof that is of smaller cross section than will allow ink to fiow therethrough.

2. A plug adapted for insertion at the rear end of a ball point ink reservoir tube to prevent leakage of ink at said rear tube end while venting the rear end of the tube to the atmosphere, said plug comprising a unitary flexible plastic element having an intermediate shank portion connecting end portions of semi-circular cross section that are mated to form a composite cylindrical plug body upon doubling of said element at said shank portion, the mating face of one of said end portions having a recess formed therein and the mating face of the other of said end portion having a registering lug formed thereon for maintaining said end portions in mated relation, and the mating face of said other end portion also having at least one groove for-med therein that extends throughout the length of said end portion and that is of smaller cross section than will allow ink to flow therethrough.

37 A plug adapted for insertion at the rear end of a ball point ink reservoir tube to prevent leakage of ink at said rear tube end while venting the rear end of the tube to the atmosphere, said plug comprising a unitary flexible plastic element having an intermediate shank portion connecting end pontions of semi-circular cross section that are mated to form a composite cylindrical plug body upon doubling of said element at said shank portion, said shank portion being notched midway of its length at the side thereof opposite the mating faces of said end portions for facilitating the doubling of said body to form said composite plug body, and the mating face of one of said end portions having a groove therein that extends throughout the length of said end portion and that is of smaller cross section than will allow ink to flow therethrough.

References Cited in the file of this patent UNITED STATES PATENTS 1,291,671 Roll Ian. 14, 1919 2,639,839 Sokolik May 26, 1953 FOREIGN PATENTS 636,147 Great Britain Apr. 26, 1950 1,002,407 France Oct. 31, 1951 1,066,416 France Jan. 20, 1954 

